| 摘要 |
PURPOSE:To output a sound signal with excellent sound quantity by using a band pass filter so as to extract a sound intermediate frequency signal and a video intermediate frequency signal from an output signal of an intermediate frequency amplifier so as to exclude an undesired disturbing signal. CONSTITUTION:A video band pass filter 7 and a sound band pass filter 8 are set respectively to a narrow band through which a video intermediate frequency and a sound intermediate frequency pass and an undesired disturbing signal other than the video intermediate frequency signal and the sound intermediate frequency signal is eliminated. Further, the 1st AGC voltage applies automatic gain control to the base band video signal and the 2nd AGC voltage applies the automatic gain control of the sound intercarrier signal, then the level of the base band video signal and the level of the sound intercarrier signal are made respectively constant and the level difference between the base band video signal and the sound intercarrier signal is made to a desired value. Thus, no disturbing signal is superimposed on the sound signal demodulated and outputted to improve the sound quality.
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